Birds chemical defenses

In addition to their role in chemical defense, DMSP-lyase products may also function as chemical cue in more complex trophic cascades. In the natural environment DMS-production is related to zooplankton herbivory [60] and can thus act as an indicator for the availability of food for planktivorous birds. Indeed, some Antarctic Procellariiform seabirds can detect DMS (22) and are highly attracted to the cue, as was shown with DMS-scented oil slicks on the ocean surface [61]. The odors released during zooplankton grazing (DMS) as well as those of zooplankton itself (e.g., trimethylamine and pyrazines) are attractive to birds [62], thus assisting vertebrate search behavior. 

Dumbacher, J. P. (2003). Natural histoiy of chemical defense in New Guinea birds. InPro-ceedings of the 10th International Symposium on Chemical Signals in Vertebrates, July, 2003, Oregon State University, Corvallis. 

Monarch butterflies t.g., Danaus plexipus) combine two sets of natural compounds. Larvae feed on plants rich in cardiac glycosides and use them as chemical defense compounds. Adult butterflies visit plants with PAs, where they collect PAs that are converted to pheromones or transferred to their eggs 4,17,31,33,361,515). A similar PA utilization scheme was observed with larvae of the moth Utetheisa ornatrix 367,516), where the compounds were shown to be deterrent for spiders and birds 225, 525). The chrysomelid beetle Oreina feeds on PA-containing plants, such as Adenostyles, and stores the dieUuy PAs in the defense fluid 463,524). 

Dumbacher JP, Beehler BM, Spande TE, Garraffo HM, and Daly JW (1992) Homobatrachotoxin in the genus Pit-ohui Chemical defense in birds Science 258 799-801. 

Dumbacher, J.P. et al. 1992. Homobatra-chotoxin in the genus Pitohui Chemical defense in birds Science 258 799-801. SeealsolettertotheeditorbyJ.I. Glendin-ning, 1993. Pitohui How toxic and to whom Sciencez 582 J.P. Dumbacher etai. 1993. Science-Lyy-. 582-583. 

Some animals, as well, use toxins to defend themselves. Some poisonous toads and frogs can synthesize toxins. Others acquire their chemical defenses from plants they eat. The Monarch butterfly is probably the best example of this. The larvae eat milkweed leaves and the toxins are retained in their bodies. The toxins are still there after metamorphosis from larva to butterfly. Birds that eat Monarch butterflies regurgitate their prey and quickly learn to avoid others of the same species. 

In other words methlocarb reduced bird damage, as measured by observations of missing and damaged sprouts, but also may have carried with It some phytotoxic effects. Thus, It may be that, as with some plants that have developed their own chemical defenses, the addition of a chemical repellent to a crop may only be advantageous under conditions of high levels of herbivore predation. 

How much a mammal eats of a given plant often depends on the levels of different classes of chemical constituent, notably nutrients and plant secondary metabolites. As in birds, it is not the plant defense compounds alone, but rather complex balances between nitrogen and carbohydrate contents, levels of defense compounds, and fiber that determine palatability. 

Fig. 94.4 When disturbed, e.g., by birds or other predators, the pine sawfly Diprion pini larva shows a rapid defense movement and discharges a droplet of resin which is chemically identical mixture of mono- and diterpenes as resin produced by the pine host Pinus sylvestris...

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